Influences of thickness-uniformity and surface morphology on the electrical and optical properties of sputtered CdTe thin films for large-area II-VI semiconductor heterostructured solar cells

It is well known that, theoretically, thin-film cadmium telluride (CdTe) solar cell technology can improve on the conversion efficiency and production costs of conventional silicon solar cell technology. Due to the optimal band gap energy (about 1.4 eV) for solar energy absorption, high light absorption capability and lower cost requirements for solar cell production, CdTe has been widely researched as being suitable for commercial cell production. In this study, the sputtering method, which can improve on the cost-efficiency and mass-production of solar cells, was employed to deposit the CdTe thin film with various processing conditions such as sputtering power, and gas pressure. The effects of the processing conditions on the thickness-uniformity and surface morphology of the CdTe thin films were investigated using atomic force microscope (AFM) and ellipsometry for large-area solar cells. The photovoltaic properties of CdTe thin films were analyzed in relation to the different thickness-uniformity and surface morphology caused by the various process conditions. The thickness-uniformity, which was controlled by the process conditions in the sputtering process, was found to affect the photovoltaic properties of the sputtering-deposited CdTe thin films. Higher carrier concentration and better optical absorbance were obtained in CdTe thin films with a good thickness-uniformity.